But judges in London ruled against the charity in November last year, saying they were "not persuaded" its case was made out.

The charity has now been given permission to challenge that decision at the Court of Appeal.

Law firm Leigh Day, which is representing the charity, said on Thursday there are currently 3,350 unaccompanied children in Greece and that, to date, only one child has been relocated in the UK under the Dubs Amendment.

Rosa Curling, a human rights solicitor at the firm, said: "We are pleased the Court of Appeal has listened to the concerns raised by our clients who believe the Government needs to reopen the consultation so that national capacity to assist these lone children, many of whom are struggling to survive and at risk of serious abuse, can be properly assessed."

Migrants and refugees on the island of Kos, Greece (Jonathan Brady/PA)

Help Refugees founder and chief executive Josie Naughton said: "We are delighted that permission to appeal has been granted.

"The crisis these children are facing is still as desperate now as it was when the amendment was passed."

The charity also launched a campaign to help finance its case against the Home Office on the CrowdJustice fundraising website.

Ms Naughton added: "The Dubs campaign was the greatest public pressure to help refugees in this country in generations.

"Now we're asking for the British public's help to fund this case and help hold the Government to account on their unfulfilled legal responsibility to provide sanctuary to unaccompanied children."

The Government previously defended the claim at the High Court, arguing there was no illegality in the consultation process.

The Dubs Amendment was to the 2016 Immigration Act and, from May last year, required the Home Secretary to make arrangements to relocate "a specified number" of vulnerable refugee children from Europe based on feedback from local authorities.

AMBER RUDD CONCEDES ON CHILD REFUGEES' ELIGIBILITY FOR DUBS

We are absolutely thrilled to hear that, after almost two years of incredible public pressure, another arbitrary restriction on child refugees' eligibility for the Dubs Amendment has been lifted. pic.twitter.com/aw3KNLUzHt

Ms Curling previously said the charity's litigation has already led to an extra 130 places from the original 350 specified by the Government.

Help Refugees said the Government has also changed its criteria that only children who had been in Europe since before March 2016 would be eligible under the scheme, and will now take in children who arrive before March of this year.

The charity's crowdfunding page can be found at www.crowdjustice.com/case/dubs-now